The present invention relates to a lubricating device for the raceway of the bobbin case of a rotary sewing machine looptaker whose body has a recess, formed by a bottom and an essentially cylindrical sidewall, for holding the bobbin case. The hub of the looptaker has an oil collecting chamber comprising an annular cavity with undercut inside peripheral area. This chamber receives the oil supplied from an oil collecting sump. Centrifugal action causes the oil to flow through a conduit, located between the oil collecting chamber and the bottom of the recess, via a adjusting device to the raceway for the bobbin case.
It is the purpose of the present invention to provide the raceway of the bobbin case of a rotating looptaker with an adequate but not excessive amount of lubricant, both immediately after starting the sewing machine and at a high rpm, with the required amount of lubricant adjustable by simple adjusting means.
There are already known in the art lubricating devices for rotating looptakers equipped with an adjusting device for metering the lubricant delivered to the raceway of the bobbin case.
Thus, from the German Utility Pat. No. 1,716,619 there is known a device for looptaker lubrication where the amount of lubricant delivered by capillary action to the looptaker is set by a setscrew varying the cross-section of the wick located in a plastic hose. This setscrew is in the vicinity of the oil reservoir.
There are also known looptaker lubricating devices for looptakers rotating about a vertical axis, e.g., from the German Patent Document 831,187 where the oil in a reservoir is pumped by means of a pump into the hollow looptaker shaft and delivered to a wick located in the borehole of the looptaker shaft and terminating in the looptaker "basket". The amount of oil can be adjusted by a valve screw with a conically pointed end. This screw is located in the line connecting the pump to the bottom end of the hollow shaft.
With these known lubricating devices, the setting of an accurately metered oil quantity is very time consuming since the looptaker, because of the oil supply in the wick, must run for quite a while till a changed setting has an effect.
From the U.S. Pat. 2,659,331, there is known a looptaker lubricating device where a lubricant reservoir in the form of a cylindrical ring is fastened coaxially on the looptaker and connected to the raceway of the looptaker by means of a lubricant line on the periphery of the ring. Adjustment is made by a screw which can be turned into the inside of the lubricant line; by varying the cross-section. This screw causes a change of the rate of the flow of the lubricant.
Another adjusting device based on the principle of cross-sectional variation has been proposed in the German Patent Application No. P 6123 Cl. 52a, 57/05 for lubricating a looptaker which is connected directly or indirectly with a rotating oil catching receptacle in the form of a truncated hollow cone. Through a supply pipe which runs parallel to the looptaker shaft and is equipped with an adjusting device in the form of a faucet, the oil flows into the catching receptacle and is moved by the centrifugal force, arising during rotation of the looptaker, through one or several channels to the bobbin case raceway.
According to the German Pat. 1,158,799, a looptaker lubricating device which permits sensitive and immediate regulation of the oil flow in the immediate vicinity of the looptaker raceway and which prevents a flooding of the looptaker raceway when the machine stops can be provided as follows: The end of a supply pipe, running parallel to the looptaker shaft and connecting the oil collecting chamber, open at the rear and fastened to the looptaker hub, to the bottom of the looptaker, projects into the bottom of the looptaker only so far that the head of an adjustment screw fastened into the supply pipe is completely within the opening in the bottom of the looptaker.
With these lubricating devices, known from the lastmentioned patents, for the raceway of the bobbin case, the adjusting means for the lubricant supply are in the immediate vicinity of the point of lubrication so that a sensitive and immediate metering of the oil supply is achieved.
With lines, located inside the looptakers to supply oil, of relatively small cross-section, there is danger of adding fillers separated by the needle during sewing and by the cloth feeder from the cloth (dressing glue, etc.), so that these channels frequently have to be unclogged by means of a wick. This hazard increases if these channel cross-sections or lines are narrowed considerably by the proposed adjusting means. Accordingly, the channels must be cleaned very frequently after the adjusting screw has been removed or the faucet is opened; as a result, the previously determined accurate setting to the desired flow rate becomes lost.
It is an object of the present invention to provide a lubricating device suitable for looptakers rotating about a vertical or a horizontal axis which makes it possible to deliver an accurately metered and constant oil quantity to the raceway for the bobbin case, without the use of wicks and adjusting means narrowing the oil supply channels.
Another object of the present invention is to provide a lubricating device of the foregoing character which is substantially simple in construction and may be economically fabricated.
A further object of the present invention is to provide a lubricating arrangement, as described, which may be readily maintained in service, and which has a substantially long operating life.